Card Decks have been a part of Warhammer Underworlds that may have seemed like a barrier to new players. Older gamers have years of cards at their disposal while new players do not. The Rivals system, coming in Harrowdeep, looks to even the playing field a bit with pre-built decks for you to use.
From the article:
When we revealed Warhammer Underworlds: Harrowdeep at Gen Con, we touched upon the new Rivals format that the new season introduces. We’re now at liberty to go into more detail on Rivals, which has been designed as the best way to get started with Warhammer Underworlds. Here’s what you need to know.